1. Technical Field
The present invention relates to a method and apparatus for indicating with the aid of a measuring instrument, the deviation or discrepancy between actual and criterion values, preferably in setting a course for a vehicle, the instrument having an indicator at least for the criterion value, which consists of one or more measured values, which are dependent on factors affecting the propulsion of the vehicle.
2. Background Art
In navigation there are different aids of both analogue and digital type. Common to the analogue devices is that they are equipped with scales having numerical marking towards which the indicators point. The numerical values pointed out by the indicators then form the basis for assessing the course of the vehicle, and thus the deviation from the desired course. The digital devices often have at least two separate value displays denoting the actual and the desired course, from which the deviation from the latter can be assesed. This deviation is sometimes given directly as a digital difference value display.
The known apparatus for indicating the discrepancy between desired and actual value are thus based on a method where numerical values must be read off for assessing the deviation. It has been found, however, that incorrect readings are easily taken, particularly in situations where the observer is subjected to stress, as with rapidly moving vehicles such as aircraft, or in situations occurring in competion sailing. In such situations there is a risk that even the zero value on a digital difference value display may be incorrectly read, i.e. the zero indicating that the vehicle is on course has been taken to be an 8 instead of a 0, resulting in departure from the correct course.